Deoxidation of copper

ABSTRACT

A process is provided for the gaseous deoxidation of copper either by the injection of liquid methanol, methanol vapor or hydrogen plus carbon monoxide from methanol cracking as a reducing agent beneath the surface of the molten metal as a poling fluid or by introducing liquid methanol, methanol vapor or hydrogen plus carbon monoxide from methanol cracking as a reducing vapor above the surface of the molten metal or both.

United States Patent [191 Sherman [451 Oct. 29, 1974 DEOXIDATION OF COPPER [75] Inventor: James Leonard Sherman,

Woodstown, NJ.

[73] Assignee: E. I. du Pont de Nemours and Company, Wilmington. Del.

[22] Filed: Feb. 28, 1973 [21] Appl. No.: 336,764

OTHER PUBLICATIONS Karrer, P.; Organic Chemistry, New York. I938. pp. 77, (Methyl Alcohol).

Kirk-Othmer'; Encyclopedia of Chemical Technology. New York, I963, (Methanol).

Primary Examiner-Walter R. Satterfield [57] ABSTRACT A process is provided for the gaseous deoxidation of copper either by the injection of liquid methanol, methanol vapor or hydrogen plus carbon monoxide from methanol cracking as a reducing agent beneath the surface of the molten metal as a poling fluid or by introducing liquid methanol, methanol vapor or hydrogen plus carbon monoxide from methanol cracking as a reducing vapor above the surface of the molten metal or both.

6 Claims, No Drawings DEOXIDATION or COPPER BACKGROUND OF THE INVENTION In order to remove unstable impurities from molten copper during the course of refining operations, the molten copper is first subjected to an oxidation treatment which is generally accomplished by blowing air or oxygen through the molten metal. By the time the unstable impurities have been substantially oxidized to products which vaporize or rise to the surface of the bath from whence they are removed by skimming, the molten copper generally contains significant quantities of oxygen such as, for example, 0.6 to 0.9 percent. In order to reduce and possibly even eliminate the oxygen content from the molten copper it has long been the practice to employ a technique known as poling which consists of immersing poles of green wood into the molten copper base metal. The volatilization of gases from the green wood creates substantial turbulence in the molten metal and at the same time effects a chemical reduction of any oxides present in the molten bath.

Although the use of green wood in the poling of copper is a somewhat archaic practice which is expensive, cumbersome, awkward and dangerous, nevertheless because such process has been reliable and effective, it is still being used today. While various attempts have been made to provide suitable alternatives to the archaic practice of poling" with green wood, no really satisfactory alternative has been suggested. In this regard, the use of reformed gas prepared from natural gas has been suggested in a patent assigned to Phelps- Dodge (US. Pat. No. 2,989,397). While the procedure disclosed in the Phelps-Dodge patent is effective, nevertheless it requires a large capital investment for gas reforming equipment which operates only a fraction of each day. In order to obviate this inherent disadvantage of the Phelps-Dodge process, several variations have been, proposed such as, for example, those described in US. Pat. No. 3,545,962 issued to Themelis et al. on Dec. 8, 1970; US. Pat. No. 3,619,177 issued to Beck on Nov. 9, 1971; US. Pat. No. 3,623,863 issued to Henderson et al., on Nov. 30, 1971 and the like. In each case, a variation of the use of a reformed gas formed in situ in the molten metal is disclosed.

As an alternative to the use of reformed gases generally, Czechoslovakian Pat. No. 91,406 teaches the use of anhydrous ammonia as a reducing gas for copper. In the ammonia process, the ammonia is sparged at a low rate about 12 inches below the surface of the copper. The ammonia dissociates into nitrogen and hydrogen and the hydrogen combines with the residual oxygen in the copper. Such a process is capable of reducing the oxygen content of copper to from about 0.03 to 0.08 percent from a level of 0.9 percent. Ammonia, how ever, is a strong irritant to the skin, eyes and respiratory tract and must be confined under pressure or refrigerated. It therefore requires special and expensive equipment and precautions to be taken in handling. Many problems are involved in metering and delivering the ammonia to the copper melt once the ammonia has been transported by a tank truck to a plant site. An additional problem inheres in working out a suitable method for disposing of the liquid remaining in the unloading hose at the conclusion of the operation. It is therefore readily apparent'that some improved method must be devised in order to reduce or eliminate the oxygen content of molten copper during the refining process in a safe, efficient and economical manner.

STATEMENT OF THE INVENTION The oxygen content of molten copper can be drastically reduced and even eliminated by a safe, simple method which comprises introducing liquid methanol, methanol vapor or the products of methanol cracking beneath the surface or directly above the surface of the molten copper or both. Since methanol is easily transportable and storable as well as convenient, stable against decomposition and sublimation, and does not require elaborate equipment or operating procedures in its use or handling, the use of methanol in the deoxidation of copper appears to answer every problem involved in such a treatment.

DETAILED DESCRIFTION OF THE INVENTION In accordance with this invention, methanol can be used expeditiously in deoxidizing a copper melt whether liquid methanol and/or methanol vapors and- /or the product of methanol cracking is employed.

Accordingly, unless otherwise specifically indicated, the term methanol, wherever used hereinafter, is intended to include methanol fluid (liquid and/or vapors) and the products of methanol cracking. In the instance in which liquid methanol is used, whether the methanol liquid is injected beneath the surface of the molten copper or introduced directly above the surface of the mo]- ten copper the methanol will quickly dissociate into hydrogen and carbon monoxide because the temperature of the molten copper approaches several thousands of degrees. A similar result for the same reason is achieved when methanol vapor is introduced either below the surface or directly above the surface of the molten copper. In the third case in which the product of methanol cracking is employed, the dissociation of methanol into carbon monoxide and hydrogen has already been achieved before introduction to the molten copper. In any event, the constituents of the decomposed methanol readily react to reduce the oxygen in the copper bath without the addition of a catalytic agent of any kind. As the reducing gas mixture passes through the bath and reacts with the copper oxides, water vapor, carbon dioxide and other products are formed which volatilize through the surface of the bath and are then removed. Since methanol is easy to use and neither its decomposition products or the products of the reduction reaction are noxious, toxic, pollutants or even an annoyance, substantially all of the disadvantages of the prior art are effectively obviated by the use of methanol to deoxidize copper.

The actual mechanics of carrying out the process of the instant invention are relatively simple. The conversion of methanol to carbon monoxide and hydrogen via methanol cracking is readily accomplished and the operation of the cracking system is quite elementary. Generally speaking, a solution containing a 2:1 ratio of water to methanol is vaporized and passed over a heated catalyst at approximately 350C. The catalyst cracks the methanol and releases carbon monoxide and hydrogen. The cracking of methanol can be achieved elsewhere and the products of the methanol cracking can be transported to the site at which they are to be used or else the methanol cracking process can take place on the site and the products of the cracking process can be introduced directly to deoxidize the copper melt.

While any desired apparatus may be used in the deoxidation of copper in accordance with this invention, it is preferred that a substantially closed furnace be employed and that any of the access openings with which the furnace is provided are closed before the poling or deoxidation step is initiated in order to prevent the entry of air into the atmosphere above the copper melt. Notwithstanding, it is also possible and even preferred to maintain an atmosphere of methanol vapors above the surface of the melt and/or to introduce the methanol vapors or the product of methanol cracking below the surface of the copper melt at a sufficient rate to provide a positive pressure in the furnace atmosphere.

The methanol may be introduced either below the surface of the copper melt or directly to the surface of the copper melt by means of any suitable expedient. It

is possible for example, to use tuyeres, lances, porous,

refractories and the like in order to achieve such a result.

The rate of delivery and the amount of methanol to be introduced into the bath is variable and is dependent on several factors including the time available for the refining cycle, the concentration of oxygen in the copper, the number and size of the injection devices used to introduce the reducing materials to the molten copper, the quantity of the copper in the bath and so on. Because the efficiency of the deoxidation of the molten copper will depend, among other things, on the establishment of a considerable contact area between the injected gas and the molten metal, it is desirable in carrying out the process of this invention to introduce the reducing expedient at a sufficient rate and pressure not only to overcome the hydrostatic pressure of the copper but also to agitate the molten copper and to form a large number of bubbles so that the interfacial surface area of contact is as large as possible.

It is also possible to accurately calculate the amount of methanol which will be consumed in reducing the oxygen content of the molten copper to the desired level once the initial oxygen content of the melt is known. For example, in order to reduce the oxygen content of a ton of copper from 0.09 to 0.05 percent, it is necessary to remove 17 pounds of oxygen.

2.000 lb./T X 0.0090 0.0005 17.0 lb./T

The oxygen scavenging effect of methanol or the decomposition products thereof can be calculated using the following equations:

CH OH 3 O CO 2 H O therefore, Methanol/Oxygen: 32/48 2/3 Thus the amount of methanol consumed per ton of copper to reduce the oxygen content from 0.90 to 0.05 percent is 2/3 X 17 or 11.3 pounds. More than this amount will generally be introduced to the melt, however, in order to efficiently carry out the process of the invention.

Progressive determinations can be made during the deoxidation process on small samples of the molten copper taken from the bath from time to time to ascertain the quantity of oxygen then still remaining in the melt. In either case conventional analytical procedures readily available to the art are used to determine the oxygen content of the copper melt.

As discussed hereinbefore, each individual embodiment of this invention may be employed exclusively or in any combination of any two of them or all together simultaneously, as desired. Indeed, while the most preferred embodiment of this invention involves the injection of methanol below the surface of the molten copper, nevertheless, it is even more preferred to simultaneously introduce methanol below the surface of the molten copper while at the same time introducing methanol above the surface of the molten copper to be deoxidized. Notwithstanding the foregoing, however, it is to be understood that the advantages to be derived by the use of methanol as described herein can be achieved even in those instances in which other expedients heretofore disclosed as useful in the deoxidation of copper are employed. For example, any of the reducing expedients discussed in any of the patents cited hereinbefore may be introduced to the surface of the molten copper while methanol is introduced below the surface of the molten metal or, alternatively, such prior art expedients may be injected into the molten metal while methanol is introduced to the surface of the molten copper. These and even further variations in the invention may be made by one skilled in the art without departing from the spirit and scope of the invention except as set forth in the claims. 1

What is claimed is:

l. A method for the deoxidation of molten copper which comprises introducing a member selected from the group consisting of liquid methanol and methanol vapor as a reducing agent to the copper melt.

2. The method of claim 1 wherein the group member is introduced below the surface of the copper melt.

3. The method of claim 1 wherein the group member is introduced above the surface of the copper melt.

4. The method of claim 1 wherein a group member is introduced below as well as above the surface of the copper melt.

5. The method of claim 1 wherein the group member is liquid methanol.

6. The method of claim 1 wherein the group member is methanol vapor. 

1. A METHOD FOR THE DEOXIDATION OF MOLTEN COPPER WHICH OMPRISES INTRODUCING A MEMBER SELECTED FROM THE GROUP CONSISTING OF LIQUID METHANOL AND METHANOL VAPOR AS A REDUCING AGENT TO THE COPPER MELT.
 2. The method of claim 1 wherein the group member is introduced below the surface of the copper melt.
 3. The method of claim 1 wherein the group member is introduced above the surface of the copper melt.
 4. The method of claim 1 wherein a group member is introduced below as well as above the surface of the copper melt.
 5. The method of claim 1 wherein the group member is liquid methanol.
 6. The method of claim 1 wherein the group member is methanol vapor. 